When it's all over, the Detective and her little offspring safe, he is free to remember.
Remember the time Mother stopped smiling, when she stopped trying, when she stood by Father's side and did nothing.
That he did the same. Let Dad banish her and cage her, as he stood by the sideline. He lets Maze torture her, knowing she won't break, won't beg and won't ask for forgiveness for what she didn't do.
He won't apologize to her, not for giving her the same treatment she gave to him, but this is different.
This is Father asking him to do something, telling him it's his time to curse her for eternal punishment. And no matter how terrified and resentful he is, he's not sure he can do that.